INPUT
Input
Input is any data or instructions entered into the memory of a computer.
The four types of input are:
Data
Data is a collection of unorganized facts that can include words, numbers,
pictures, sounds, and videos.
The term data is commonly used and accepted as both the singular and
plural form of the word.
Program
A program is a series of instructions that tells a computer how to perform
the tasks necessary to process data into information.
Command
A command is an instruction given to a computer program.
Commands can be issued by typing keywords or pressing special keys
on the keyboard.
Some programs provide menu as a means of entering commands.
Most programs today have a graphical user interface that use
icons, buttons, and other graphical objects to issue commands.
User Response
A user response is an instruction a user issue to the computer by replying to
a question posed by a computer program.
Input Devices
An input device is any hardware component that allows a user to enter data,
programs, commands, and user responses into a computer.
The Keyboard
The keyboard is one of the primary input devices on a computer.
Desktop computer keyboards usually have 101 to 105 keys.
All computer keyboards have a typing area that includes the letters of the
alphabet, numbers, punctuation marks, and other basic keys.
Many desktop computer keyboards also have a numeric keypad located on the
right side of the keyboard.
A numeric keypad is a calculator-style arrangement of keys representing
numbers, a decimal point, and some basic mathematical operators.
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Most keyboards also contain function keys across the top of the keyboard.
Function keys are special keys programmed to issue commands and
accomplish certain tasks.
The command associated with a function key depends on the program being
used.
A standard computer keyboard is sometimes called a QWERTY keyboard
because of the layout of its typing area.
A QWERTY keyboard is designed to limit typing speed in order to avoid
the levers jamming together in ordinary typewriters.
The Dvorak keyboard is a keyboard with an alternative layout designed to
improve typing speed.
This type of keyboard places the most frequently typed letters in the
middle of the typing area.
Most of today’s desktop computer keyboards are enhanced keyboards.
An enhanced keyboard has twelve function keys along the top, two CTRL
keys, two ALT keys, and a set of arrow and additional keys between the
typing area and the numeric keypad.
Many keyboards have a rectangular shape with the keys aligned in rows.
An ergonomic keyboard is the type of keyboard redesigned to minimize
the chance of repetitive strain injuries, particularly of the wrists and hands,
as well as to improve comfort and efficiency.
Pointing Devices
A pointing device is an input device that allows a user to control a pointer,
which is a small symbol on the screen.
Mouse
The mouse is the most widely used pointing device on desktop computers.
As the mouse is moved across a flat surface, the pointer on the screen
also moves.
Operations that can be executed by a mouse include:
Point – Move the mouse across a flat surface until the pointer
rests on the item of choice.
Click – Press and release the primary mouse button, which is
usually the left mouse button.
Right-click – Press and release the secondary mouse button,
which is usually the right mouse button.
Double-click – Quickly press and release the primary mouse
button twice without moving the mouse.
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Drag – Point to an item, hold down the left mouse button, move
the item to the desired location on the screen, and then release the
left mouse button.
Rotate wheel – Roll the wheel of the mouse (if any) forward or
backward.
Popular mouse types include:
A mechanical mouse is a mouse that has a rubber or metal ball
on its underside.
An optical mouse has no moving mechanical parts inside, but
uses devices that emit and sense light to detect the mouse’s
movement.
A cordless mouse or wireless mouse uses infrared or radio waves
to communicate with a receiver connected to the computer.
Trackball
A trackball is a stationary pointing device with a ball mechanism on its top.
A trackball is good for limited desk space.
However, a trackball is not as accurate as a mouse and its ball
mechanism also requires more frequent cleaning.
Touchpad
A touchpad or trackpad is a small, flat, rectangular pointing device that is
sensitive to pressure and motion.
Touchpads are more often found on laptop computers.
Pointing Stick
A pointing stick is a pressure-sensitive pointing device shaped like a pencil
eraser that was first developed by IBM for its laptop computers.
The pointing stick is positioned between keys on the keyboard.
Joystick
A joystick is a vertical level mounted on a base.
A user moves the lever in different directions to control the actions of
objects on the screen.
The level usually includes buttons called triggers so that a user can
press to activate certain events.
Touch Screen
A touch screen is a monitor that has a touch-sensitive panel on the screen.
A user interacts with the computer simply by touching different areas
of the screen.
Because it generally requires a lot of arm movements, touch screens
are not suitable to enter large amount of data.
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Touch screens are often used in kiosks located in department stores,
hotels, airports, and museums.
Pen Input
Pen input allows a user to use an electronic pen, rather than a keyboard or
mouse for input.
Light Pen
A light pen is a handheld input device that contains a light source or
can detect light.
Some light pens require a specially designed monitor to work.
Stylus
Many handheld computers also allow users to input data using an
electronic pen or stylus.
A stylus looks like a ballpoint pen but uses an electronic head
instead of ink.
Pen computers use handwriting recognition software to
translate the letters and symbols back into character data that the
computer can understand.
Graphics Tablet
A graphics tablet consists of a flat, rectangular, electronic plastic board
used to input drawings, sketches, or other graphical data.
Each location on the graphics tablet corresponds to a specific
location on the screen.
When a user draws on the tablet with either an electronic pen or a
puck, the tablet detects and converts the movements into digital
signals that are sent into the computer.
A puck is a device that looks similar to a mouse, except that
it has a window with cross hairs so that the user can see
through to the tablet.
Scanners and Reading Devices
Scanners and reading devices make the input process more efficient by capturing
data directly from source documents.
A source document is the original form of the data.
Optical Scanners
An optical scanner is a light-sensing input device that reads printed text and
graphics and then translates the results into a form the computer can use.
A scanner works like a copy machine except that it creates a file of the
document instead of a paper copy.
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When a document is scanned, the results are stored in rows and columns of
dots called a bitmap.
Each dot on a bitmap consists of one or more bits of data.
The more bits used to represent a dot, the more colors and shades
of gray that can be represented.
Most of today’s scanners range from 30 bit to 48 bit.
The resolution, or density of the dots, determines the sharpness and clarity
of the image.
Resolution is measured in dots per inch (dpi).
The more dots, the better the resolution, and the resulting image is
of higher quality.
The actual scanned resolution is known as the optical resolution.
The enhanced or interpolated resolution refers to using a
special formula to add dots between those generated by the optical
resolution to make the resolution higher.
Most of today’s scanners range from 600 to 2400 dpi.
Scanners are mainly used for image processing.
Image processing or imaging consists of capturing, storing, analyzing,
displaying, printing, and manipulating images (bitmaps).
Image processing enables organizations to convert paper
documents such as reports, memos, and procedure manuals into
an electronic form.
Optical Readers
An optical reader is a device that uses a light source to read characters, marks,
and codes, and then converts them into digital data that can be processed by a
computer.
Optical Character Recognition (OCR) Devices
Most OCR devices include a small optical scanner for reading characters
and sophisticated software for analyzing what is read.
Optical character recognition (OCR) is a technology that involves
reading typewritten, computer-printed, or handwritten characters from
ordinary documents and translating the images into a form that the
computer can understand.
OCR software compares the shapes of characters scanned with
predefined shapes stored in memory and converts the shapes into
characters the computer can understand.
OCR software can also be used with optical scanners.
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Optical Mark Recognition (OMR) Devices
OMR devices can read hand-drawn marks such as small circles or
rectangles.
The OMR device first reads a master document, and to record correct
answers based on patterns of light; the remaining documents are then
passed through the OMR device and their patterns of light are matched
against the master document.
Bar Code Scanner
A bar code scanner user laser beams to read bar codes.
A bar code is an identification code that consists of a set of vertical
lines and spaces of different widths.
Magnetic Ink Character Recognition (MICR) Reader
A MICR reader is used to read text printed with magnetized ink.
MICR is used most exclusively by the banking industry for check
processing.
Data Collection Devices
Data collection devices are designed and used to obtain data directly at the
location where the transaction or event takes place.
Data collection devices are used in factories, warehouses, or other
locations where heat, humidity, and cleanliness are difficult to control.
Digital Cameras
A digital camera allows a user to take pictures and store the photographed
images digitally instead on traditional film.
The three basic types of digital cameras are:
Studio Camera
A studio camera is a stationary camera used for professional studio work.
Field Camera
A field camera is a portable camera that has many lenses and other
attachments, which is used by photojournalists.
Point-and-shoot Camera
A point-and-shoot camera is more affordable and lightweight and provides
acceptable quality photographic images for the home or small business
users.
The quality of a digital camera is also measured by the number of bits it stores
in a dot and the number of dots per inch, or resolution.
The higher each number, the better quality, but also the more expensive.
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Audio and Video Input
Audio Input
Audio input is the process of entering music, speech, or sound effects.
A sound card is required to record high quality sound.
Sound is entered via a device such as a microphone, tape player, or audio
CD player.
External MIDI devices such as an electric piano keyboard can also connect
to the sound card for audio input.
MIDI (musical instrument digital interface) is the electronic music
industry’s standard that defines how sounds are represented
electronically by digital musical devices.
Windows stores audio files as waveforms, which are called WAV files and
have a .wav extension.
WAV files are often large and are usually compressed in order to take
up less storage space.
Speech Recognition
Speech recognition, also called voice recognition, is the computer’s capability of
distinguishing spoken words.
Speech recognition programs do not actually understand speech; they only
recognize a vocabulary of certain words, which can range from two to more
than sixty thousands.
Speech recognition programs are either speaker dependent or speaker
independent.
With speaker-dependent software, the computer makes a profile of a
user’s voice, which means that the user has to train the computer to
recognize his or her voice.
Speaker-independent software has a built-in set of word patterns, so
a user does not have to train a computer to recognize his or her voice.
Discrete speech recognition software requires a user to speak slowly and
separate each word with a short pause.
Continuous speech recognition software allows a user to speak in a
flowing conversational tone.
Speech recognition systems are often used in situations that a user’s hands
are occupied or disabled.
They are also ideal for blind or visually impaired users.
Video Input
Video input or video capture is the process of entering a full-motion recording
into a computer and storing the video on a hard disk or some other medium.
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A video capture card is required to converts the analog video signal into a
digital signal that a computer can understand.
Video is captured via a device such as a video camera, VCR, or other device
plugged into the video capture card.
Video files can require tremendous amounts of storage space and are
usually compressed.
The MPEG is a popular video compression standard defined by the
Moving Picture Expert Group.
A video digitizer can be used to capture an individual frame from a video
and then save the still picture in a file.
Videoconferencing
A videoconference is a meeting between two or more geographically separated
individuals who use a network or the Internet to transmit audio and video data.
To participate in a videoconference, a user must have a microphone,
speakers, and a video camera mounted on his or her computer.
A whiteboard is another window on the screen that display notes and
drawings simultaneously on all the participants’ screen.
It provides multiple users with an area on which they can write or
draw.
PC cameras or web cams allow the home user to see people at the same
time they communicate on the Internet.
Input Devices for Physically Challenged Users
The American with Disabilities Act (ADA) requires that any company with 15
or more employees make reasonable attempts to accommodate the needs of
physically challenged workers.
Besides speech recognition systems, several other input devices are also
available.
A keyguard, which is placed over the keyboard, allows a user with limited
hand mobility to rest his or her hand on the keyboard without accidentally
pressing any keys. It also guides the user’s finger or pointing device so that
only one key is pressed at a time.
Keyboards with larger keys and screen-displayed keyboards on which keys
are pressed using a pointing device can also help.
Small trackballs that can be controlled with a thumb or one finger can be
used.
A head-mounted pointer allows people with limited hand movement to
control the pointer or insertion point.
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